Integration Guide

Website Payments Standard Integration Guide September 2008 343
HTML Form Basics for Website Payments Standard
Instant Payment Notification – notify_url
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src="https://www.paypal.com/en_US/i/btn/btn_buynow_LG.gif"
alt="PayPal - The safer, easier way to pay online">
</form>
Instant Payment Notification – notify_url
Instant Payment Notification consists of three parts:
1. Someone pays you.
2. PayPal POSTs FORM variables to a URL you specify that runs a program to process the
variables.
3. You validate the notification.
FIGURE 11.1 How IPN Works – Three General Steps
1. A payment or a refund triggers IPN. This payment can be via Website Payments Standard
FORMs or via the PayPal Web Services APIs for Express Checkout, MassPay, or
RefundTransaction. If the payment has a “Pending” status, you receive another IPN when
the payment clears, fails, or is denied.
2. PayPal posts HTML FORM variables to a program at a URL you specify. You can specify
this URL either in your account profile or with the notify_url variable on each
transaction. This post is the heart of IPN. Included in the notification is the payment
information, such as the payer’s name and the amount paid. All possible variables in IPN
posts are detailed in the Order Management Integration Guide
.When your server receives a
notification, it must process the incoming data.
3. Your server must then validate the notification to ensure that it is legitimate. For details, see
the Order Management Integration Guide
.